More particularly, the invention relates to a hinge mechanism comprising:                first and second frames rotatably mounted in relation to each other about an axis of rotation,        a geared adjustment device connecting the first and second frames together to allow adjustment of a relative angular position of said first and second frames, said adjustment device comprising:                    at least one first set of gear teeth integral with the second frame, and forming at least one arc of a circle centered on the axis of rotation,            at least one first toothed component capable of engaging with said first set of gear teeth and mobile in relation to said first frame, between on the one hand a locking position in which it cooperates with the first set of gear teeth of the second frame in order to immobilize the first and second frames in relation to each other and on the other hand, a retracted position in which said locking component does not interfere with the gear teeth of the second frame,            and an actuation device capable of controlling the adjustment device.                        
FR-A-2 790 230 describes an example of such a hinge mechanism, comprising moreover overlooking elements held by the first frame that interfere with the second frame when the torque applied between the first and second frames exceeds a predetermined threshold when the actuation device is idle, in order to immobilize the first and second frames rotatably in relation to each other with increased resistive torque.
This hinge mechanism gives complete satisfaction. In particular, the action of the overlooking elements makes it possible to increase the mechanical strength of the hinge mechanism, in particular in the event of a road accident when this mechanism is used in a vehicle seat. However, this principle requires the installation of additional parts in the first frame.